U.S. patent number 5,324,783 [Application Number 07/865,212] was granted by the patent office on 1994-06-28 for golf ball cover compositions.
This patent grant is currently assigned to Lisco, Inc.. Invention is credited to Michael J. Sullivan.
United States Patent |
5,324,783 |
Sullivan |
* June 28, 1994 |
Golf ball cover compositions
Abstract
The present invention is directed to improved cover compositions
for golf ball construction and the resulting intermediate modulus
golf balls produced utilizing the improved cover compositions. The
novel golf ball cover compositions of the invention comprise a
blend of a relatively large amount of hard ionomeric resins, and a
relatively low (i.e. from about 10 to about 25-30 process) amount
of soft ionomers. When the cover compositions of the invention are
utilized to manufacture golf balls, the golf balls produced
thereby, exhibit properties of improved distance without
sacrificing playability and/or durability characteristics when
compared to known hard-soft ionomer blends.
Inventors: |
Sullivan; Michael J. (Chicopee,
MA) |
Assignee: |
Lisco, Inc. (Tampa,
FL)
|
[*] Notice: |
The portion of the term of this patent
subsequent to December 5, 2006 has been disclaimed. |
Family
ID: |
24232588 |
Appl.
No.: |
07/865,212 |
Filed: |
April 8, 1992 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
559177 |
Jul 27, 1990 |
5120791 |
|
|
|
Current U.S.
Class: |
525/196; 473/385;
524/908; 525/221; 525/222; 525/330.2; 525/919 |
Current CPC
Class: |
A63B
37/0003 (20130101); C08L 23/08 (20130101); A63B
37/0024 (20130101); A63B 37/0031 (20130101); A63B
37/0037 (20130101); A63B 37/0074 (20130101); C08L
23/08 (20130101); C08L 23/0876 (20130101); C08L
2205/02 (20130101); Y10S 525/919 (20130101); Y10S
524/908 (20130101); C08L 2666/04 (20130101) |
Current International
Class: |
A63B
37/00 (20060101); C08L 23/00 (20060101); C08L
23/08 (20060101); A63B 037/12 (); C08K 003/14 ();
C08K 003/30 (); C08L 033/02 () |
Field of
Search: |
;525/196,221,222,330.2,919 ;273/235R ;524/908 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
E I. Du Pont de Nemours & Co., Inc., "Ionomer Blends for Golf
Ball Covers," Research Disclosure #27103, Kenneth Mason
Publications Ltd., Nov. 1986..
|
Primary Examiner: Seidleck; James J.
Assistant Examiner: Hamilton, III; Thomas
Parent Case Text
This is a continuation-in-part application of co-pending U.S.
application Ser. No. 559,177, filed on Jul. 27, 1990, now U.S. Pat.
No. 5,120,791.
Claims
Having thus described the preferred embodiments, the invention is
now claimed to be:
1. A golf ball comprising a core and a cover, wherein said cover
comprises:
from about 90 to about 70 percent by weight of a hard ionomer which
is a sodium or zinc salt of the copolymer of an olefin having from
2 to 8 carbon atoms and an unsaturated monocarboxylic acid having
from 3 to 8 carbon atoms, wherein said hard ionomer has a hardness
greater than 50 on the Shore D scale and a flexural modulus of from
about 15,000 to about 70,000 psi; and,
from about 10 to about 30 percent by weight of a soft ionomer which
is a sodium or zinc salt of a terpolymer of an olefin having 2 to 8
carbon atoms, methacrylic acid and an unsaturated monomer of the
acrylate ester class having from 1 to 21 carbon atoms, wherein said
soft ionomer has a hardness from about 20 to about 40 on the Shore
D scale and a flexural modulus of from about 2,000 to 10,000
psi.
2. The golf ball of claim 1, wherein the hard ionomer is a sodium
or zinc salt of the copolymer of ethylene and methacrylic acid.
3. The golf ball of claim 1, wherein said cover composition
comprises from about 90 to about 75 percent by weight of the hard
ionomer and from about 10 to about 25 by weight percent of the soft
ionomer.
4. The golf ball of claim 2, wherein said cover composition
comprises from about 90 to about 75 percent by weight of the hard
ionomer and from about 10 to about 25 by weight percent of the soft
ionomer.
5. The golf ball of claim 1, wherein said cover composition
comprises from about 75 percent by weight of the hard ionomer and
from about 25 percent by weight of the soft ionomer.
6. The golf ball of claim 2, wherein said cover composition
comprises from about 75 percent by weight of the hard ionomer and
from about 25 percent by weight of the soft ionomer.
7. A golf ball comprising a core and a cover, wherein said cover
comprises a blend of from about 90 to about 70 percent by weight of
a methacrylic acid based hard ionomer and from about 10 to about 30
percent by weight of a methacrylic acid based soft ionomer.
8. A golf ball comprising a core and a cover, wherein said cover
comprises a blend of from about 90 to about 75 percent by weight of
a hard ionomer which is a sodium or zinc salt of an
ethylene-methacrylic acid copolymer and from about 10 to about 25
percent by weight of a soft ionomer which is a sodium or zinc salt
of an ethylene, methacrylic acid, methyl or butyl acrylate
terpolymer.
9. The golf ball of claim 8, wherein the hard ionomer is a blend of
from about 75 weight percent of an ethylene-methacrylic acid
copolymer which is neutralized with a zinc ion and from about 25
weight percent of an ethylene-methacrylic acid, methyl or butyl
acrylate terpolymer which is neutralized with a sodium ion.
10. The golf ball of claim 1, wherein said cover comprises a
mixture of one or more pigments, an optical brighteners and/or
dye.
11. The golf ball of claim 7, wherein said cover comprises a
mixture of one or more pigments, an optical brighteners and/or
dye.
12. The golf ball of claim 8, wherein said cover comprises a
mixture of one or more pigments, an optical brighteners and/or dye.
Description
BACKGROUND OF THE INVENTION
The present invention concerns improved hard-soft ionomeric resin
mixtures (or blends) which are particularly well suited for the
formulation of the cover composition of a golf ball.
More specifically, the present invention relates to novel golf ball
cover compositions of intermediate modulus comprising blends of
about 90 to about 70 (preferably from about 90 to about 75) weight
percent of hard ionomer resins and from about 10 to about 30
(preferably, from about 10 to about 25) weight percent of soft
ionomer resins. The new compositions of the present invention, when
utilized for golf ball construction, particularly the construction
of two piece golf balls, produce golf balls exhibiting enhanced
travel distance and/or playability characteristics without
sacrificing the properties of roundness, impact resistance and/or
durability.
Ionomeric resins are polymers containing interchain ionic bonding.
As a result of their toughness, durability, and flight
characteristics, various ionomeric resins sold by E.I. DuPont
deNemours & Company (see U.S. Pat. No. 4,884,814) under the
trademark "Surlyn.RTM." and more recently, by the Exxon Corporation
(see U.S. Pat. No. 4,911,451) under the trademarks "Escor.RTM." and
the tradename "Iotek", have become the materials of choice for the
construction of golf ball covers over the traditional "balata"
(trans polyisoprene, natural or synthetic) rubbers. The softer
balata covers, although exhibiting enhanced playability properties,
lack the durability necessary for repetitive play.
Ionomeric resins are generally ionic copolymers of an olefin such
as ethylene and a metal salt of an unsaturated carboxylic acid,
such as acrylic acid, methacrylic acid, or maleic acid. Metal ions,
such as sodium or zinc, are used to neutralize some portion of the
acidic groups in the copolymer resulting in a thermoplastic
elastomer exhibiting enhanced properties, i.e. improved durability,
etc., for golf ball cover construction over balata. However, the
advantages gained in increased durability have been offset to some
degree by the decreases produced in playability. This is because
although the ionomeric resins are very durable, they tend to be
very hard when utilized for golf ball cover construction, and thus
lack the degree of softness required to impart the spin necessary
to control the ball in flight.
As a result, while there are currently more than fifty commercial
grades of ionomers available from DuPont and Exxon with a wide
range of properties which vary according to the type and amount of
metal cations, molecular weight, composition of the base resin
(i.e. relative content of ethylene and methacrylic and/or acrylic
acid groups) and additive ingredients such as reinforcements, etc.,
a great deal of research continues in order to develop golf ball
cover compositions exhibiting not only the improved impact
resistance and carrying distance properties produced by the "hard"
ionomeric resins, but also the playability (i.e. "spin")
characteristics previously associated with the "soft" balata
covers, properties which are still desired by the more skilled
golfer.
In various attempts to produce such an ideal golf ball, the golfing
industry has blended the hard ionomeric resins with a number of
softer polymeric materials, such as softer polyurethanes. However,
the blends of the hard ionomer resins with the softer polymeric
materials have generally been dissatisfactory in that these balls
exhibit numerous processing problems. In addition, the balls
produced by such a combination are usually short on distance.
In addition, various "hard-soft ionomeric blends", i.e. mixtures of
ionomer resins which are significantly different in hardness and/or
flexural modulus, have been attempted. However, until the
development of the specific blend combination set forth in U.S.
Pat. No. 4,884,814, directed to relatively low modulus golf ball
cover compositions, these balls were not particularly commercially
viable. In this regard, although the balls produced using the
hard-soft ionomer blends exhibited enhanced playability
characteristics, they lacked the durability needed for continuous
play.
U.S. Pat. No. 4,884,814, one of the inventor's previous patents, is
directed to the finding that if various "hard" methacrylic acid
based ionomer resins (i.e. those ionomer resins having a hardness
of about 60 to 66 on the Shore D scale as measured in accordance
with ASTM method D-2240) were blended with similar or larger
quantities of one or more "soft" ionomer methacrylic acid based
ionomer resins (i.e. those ionomer resins having a hardness from
about 25 to 40 as measured on the Shore D scale) that relatively
low modulus golf ball cover compositions could be produced that are
not only softer than the prior art hard ionomer covers but also
exhibit a sufficient degree of durability for repetitive play.
These relatively low modulus cover compositions were generally
comprised of from about 25 to about 70 percent of hard ionomer
resins and from about 30 to about 75 percent of soft ionomer
resins.
As a result, a golf ball covered in accordance with the "hard-soft"
methacrylic acid based ionomer blends of the '814 patent, exhibits
properties of enhanced playability (i.e. softness and spin) and
durability. However, notwithstanding the above, some sacrifice in
carrying distance is also exhibited in comparison with the balls
produced utilizing the hard ionomer resins.
The present invention is directed to new golf ball cover
compositions which exhibit properties of enhanced carrying distance
(i.e. possess higher coefficient of restitution values) than the
hard-soft ionomer blends set forth in U.S. Pat. No. 4,884,814,
without sacrificing characteristics such as playability (i.e.
softness and spin) and/or durability. It has been found that these
properties can be produced using improved hard-soft ionomer blends
in order to produce an intermediate modulus golf ball cover.
SUMMARY OF THE INVENTION
The present invention is directed to intermediate modulus cover
compositions for golf ball construction and the resulting golf
balls produced utilizing the improved cover compositions. The novel
golf ball cover compositions of the invention comprise a blend of
about 90 to about 70 (preferably from about 90 to about 75) weight
percent of hard ionomeric resins and from about 10 to about 30
(preferably from about 10 to about 25) of soft ionomer resins. In a
more preferred embodiment of the invention, the soft ionomer resin
is a methacrylic acid based soft ionomer resin. When the cover
compositions of the invention are utilized to manufacture golf
balls, the golf balls produced thereby exhibit properties of
improved distance without sacrificing playability and/or durability
characteristics when compared to known hard-soft ionomer
blends.
Two of the principal properties involved in the performance of golf
balls are resilience and hardness. Resilience is determined by the
coefficient of restitution (C.O.R.), the constant "e" which is the
ratio of the relative velocity of two elastic spheres after direct
impact to that before impact. As a result, the coefficient of
restitution (i.e. "e") can vary from zero to one, with one being
equivalent to an elastic collision and zero being equivalent to an
inelastic collision.
Resilience (C.O.R.), along with additional factors such as clubhead
speed, angle of trajectory, and ball configuration (i.e. dimple
pattern), generally determines the distance a ball will travel when
hit. Since clubhead speed and the angle of trajectory are not
factors easily controllable, particularly by golf ball
manufacturers, the factors of concern among manufacturers are the
coefficient of restitution (C.O.R.) and the surface configuration
of the ball.
The coefficient of restitution (C.O.R.) in solid core balls is a
function of the composition of the molded core and of the cover. In
balls containing a wound core (i.e. balls comprising a liquid or
solid center, elastic windings, and a cover), the coefficient of
restitution is a function of not only the composition of the center
and cover, but also the composition and tension of the elastomeric
windings. Although both the core and the cover contribute to the
coefficient of restitution, the present invention is directed
solely to the coefficient of restitution which is affected by the
cover composition.
In this regard, the coefficient of restitution of a golf ball is
generally measured by propelling a ball at a given speed against a
hard surface and measuring the ball's incoming and outgoing
velocity electronically. As mentioned above, the coefficient of
restitution is the ratio of the outgoing velocity to incoming
velocity. The coefficient of restitution must be carefully
controlled in all commercial golf balls in order for the ball to be
within the specifications regulated by the United States Golf
Association (U.S.G.A.). Along this line, the U.S.G.A. standards
indicate that a "regulation" ball cannot have an initial velocity
(i.e. the speed off the club) exceeding 255 feet per second. Since
the coefficient of restitution of a ball is related to the ball's
initial velocity, it is highly desirable to produce a ball having a
sufficiently high coefficient of restitution to closely approach
the U.S.G.A. limit on initial velocity, while having an ample
degree of softness (i.e. hardness) to produce enhanced playability
(i.e. spin, etc.).
The hardness of the ball is the second principal property involved
in the performance of a golf ball. The hardness of the ball can
affect the playability of the ball on striking and the sound or
"click" produced. Hardness is determined as the deformation (i.e.
compression) of the ball under various load conditions applied
across the ball's diameter (i.e. the lower the compression value,
the harder the material). As indicated in U.S. Pat. No. 4,674,751,
"softer" covers permit the accomplished golfer to impart proper
spin. This is because the softer covers deform on impact
significantly more than balls having "harder" ionomeric resin
covers. As a result, this allows the better player to impart fade,
draw, or backspin to the ball thereby enhancing playability. Such
properties can be determined by various "spin rate tests" such as
the "nine-iron" spin rate test set forth below.
Accordingly, the present invention is directed to new hard-soft
ionomer blends which produce, upon molding around solid or wound
cores to formulate a intermediate modulus cover composition, golf
balls exhibiting enhanced distance (i.e. resilience) without
adversely affecting, and in many instances, improving the ball's
playability (i.e. hardness/softness) and/or durability (i.e. impact
resistance, etc.) characteristics.
These and other objects and features of the invention will be
apparent from the following description and from the claims.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to improved cover compositions for
golf ball construction. More particularly, the present invention is
directed to improved blends of hard and soft ionomers, which, when
utilized to formulate the cover stock of golf balls, produce
intermediate modulus golf balls having enhanced properties,
including longer distance (i.e. improved C.O.R. values) with
similar or improved playability properties (i.e. similar and/or
slightly higher Riehle compression, etc.), when compared to golf
balls produced by the hard-soft ionomer blends of the prior art.
The improved properties produced by the hard-soft ionomer blends of
the present invention are due to the use of relatively low amounts
(i.e. from about 10 to about 25-30 percent) of soft ionomers, which
produce cover compositions having lower flexural modulus and
hardness (i.e. enhanced softness) and improved coefficients of
restitution when incorporated with relatively high amounts (i.e.
from about 90 to about 75-70 percent) of the hard ionomer
resins.
The hard (high modulus) ionomers suitable for use in the present
invention include those ionomers having a hardness greater than 50
on the Shore D scale as measured in accordance with ASTM method
D-2240, and a flexural modulus from about 15,000 to about 70,000
psi as measured in accordance with ASTM method D-790.
The hard ionomer resins utilized to produce the cover compositions
are ionic copolymers which are the sodium, zinc, magnesium or
lithium salts of the reaction product of an olefin having from 2 to
8 carbon atoms and an unsaturated monocarboxylic acid having from 3
to 8 carbon atoms. The carboxylic acid groups of the copolymer may
be totally or partially (i.e. approximately 15-75 percent)
neutralized.
Preferably, the hard ionomeric resins are copolymers of ethylene
and either acrylic and/or methacrylic acid, with copolymers of
ethylene and methacrylic acid being the most preferred. In
addition, two or more types of hard ionomeric resins may be blended
into the cover compositions in order to produce the desired
properties of the resulting golf balls.
Although the scope of the patent embraces all known hard ionomeric
resins falling within the parameters set forth above, only a
relatively limited number of these hard ionomeric resins are
commercially available. In this regard, the hard ionomeric resins
sold by E.I. DuPont de Nemours Company under the trademark
"Surlyn.RTM." and the hard ionomer resins sold by Exxon Corporation
under either the trademark "Escor.RTM." or the tradename "Iotek"
are examples of commercially available hard ionomeric resins which
may be utilized in the present invention in the particular
combinations described in detail below.
The hard ionomeric resins introduced under the designation
"Escor.RTM." and now sold under the new designation "Iotek" are
somewhat similar to the hard ionomeric resins sold under the
"Surlyn.RTM." trademark. However, since the "Iotek" ionomeric
resins are sodium or zinc salts of poly(ethylene acrylic acid) and
the "Surlyn" resins are zinc, sodium or lithium salts of
poly(ethylene methacrylic acid) some distinct differences in
properties exist. In addition, various blends of "Iotek" and
"Surlyn" hard ionomeric resins, as well as other available
ionomeric resins, may be utilized in the present invention.
Examples of commercially available hard ionomeric resins which may
be utilized in the present invention include the hard sodium ionic
copolymer sold under the trademark "Surlyn 8940" and the hard zinc
ionic copolymer sold under the trademark "Surlyn 9910". Surlyn 8940
is a copolymer of ethylene with methacrylic acid with about 15
weight percent acid which is about 29% neutralized with sodium
ions. This resin has an average melt flow index of about 2.8.
Surlyn 9910 is a copolymer of ethylene and methacrylic acid with
about 15 weight percent acid which is about 58% neutralized with
zinc ions. The average melt flow index of Surlyn 9910 is about 0.7.
The typical properties of Surlyn 9910 and 8940 are set forth below
in Table 1.
TABLE 1 ______________________________________ Typical Properties
of Commercially Available Hard Surlyn .RTM. Resins Suitable for Use
in the Present Invention ASTM D 8940 9910 8920 8528 9970 9730
______________________________________ Cation Type So- Zinc So- So-
Zinc Zinc dium dium dium Melt flow index, D-1238 2.8 0.7 0.9 1.3
14.0 1.6 gms/10 min. Specific Gravity, D-792 0.95 0.97 0.95 0.94
0.95 0.95 g/cm.sup.3 Hardness, D-2240 66 64 66 60 62 63 Shore D
Tensile Strength, D-638 (4.8) (3.6) (5.4) (4.2) (3.2) (4.1) (kpsi),
MPa 33.1 24.8 37.2 29.0 22.0 28.0 Elongation, % D-638 470 290 350
450 460 460 Flexural Modu- D-790 (51) (48) (55) (32) (28) (30) lus,
(kpsi) MPa 350 330 380 220 190 210 Tensile Impact D- 1020 1020 865
1160 760 1240 (23.degree. C.) KJ/m.sub.2 18225 (485) (485) (410)
(550) (360) (590) (ft.-lbs./in.sup.2) Vicat Temper- D-1525 63 62 58
73 61 73 ature, .degree.C.
______________________________________
In addition, examples of the acrylic acid based hard ionomer resins
suitable for use in the present invention sold under the "Iotek"
tradename by the Exxon Corporation include "Iotek 4000" (formerly
"Escor 4000"), "Iotek 4010", "Iotek 8000" (formerly Escor 900),
"Iotek 8020", and "Iotek 8030". The typical properties of the Iotek
hard ionomers are set forth below in Table 2.
TABLE 2 ______________________________________ Typical Properties
of Iotek Ionomers ASTM Meth- od Units 4000 4010 8000 8020 8030
______________________________________ Resin Properties Cation type
zinc zinc so- so- so- dium dium dium Melt index D-1238 g/ 2.5 1.5
0.8 1.6 2.8 10 min. Density D-1505 kg/m.sup.3 963 963 954 960 960
Melting Point D-3417 .degree.C. 90 90 90 87.5 87.5 Crystallization
D-3417 .degree.C. 62 64 56 53 55 Point Vicat Softening D-1525
.degree.C. 62 63 61 64 67 Point % Weight Acry- 16 11 lic Acid % of
Acid 30 40 Groups cation neutralized Plaque Properties (3 mm thick,
compression molded) Tensile at break D-638 MPa 24 26 36 31.5 28
Yield point D-638 MPa none none 21 21 23 Elongation at D-638 % 395
420 350 410 395 break 1% Secant D-638 MP 160 160 300 350 390
modulus Shore Hardness D-2240 -- 55 55 61 58 59 Film Properties (50
micron film 2.2:1 Blow-up ratio) Tensile at Break MD D-882 MPa 41
39 42 52 47.4 TD D-882 MPa 37 38 38 38 40.5 Yield point MD D-882
MPa 15 17 17 23 21.6 TD D-882 MPa 14 15 15 21 20.7 Elongation at
Break MD D-882 % 310 270 260 295 305 TD D-882 % 360 340 280 340 345
1% Secant modulus MD D-882 MPa 210 215 390 380 380 TD D-882 MPa 200
225 380 350 345 Dart Drop D-1709 g/ 12.4 12.5 20.3 Impact micron
______________________________________
The soft (low modulus) ionomers utilized to formulate the blends of
the present invention are acrylic acid or methacrylic acid based
soft ionomers with the methacrylic acid based soft ionomers being
the more preferred. These soft ionomers may be generally
characterized as comprised of sodium, zinc, magnesium or lithium
salts of the reaction product of an olefin having from about 2 to 8
carbon atoms, acrylic or methacrylic acid, and an unsaturated
monomer of an acrylated ester class having from 1 to 21 carbon
atoms. The carboxylic acid groups of the copolymer may be totally
or partially (i.e. about 15-75 percent) neutralized.
Preferably, the soft ionomer resins are a sodium or zinc salt of a
terpolymer of an olefin having 2 to 8 carbon atoms, either acrylic
and/or methacrylic acid, and an unsaturated monomer of an acrylated
ester class having from 1 to 21 carbon atoms, with those comprising
ethylene, methacrylic acid and methyl or butyl acrylate being the
more preferred. Moreover, two or more types of soft ionomer resins
may be blended into the cover compositions in order to produce the
desired properties of the resulting golf balls.
The soft (low modulus) ionomers suitable for use in the invention
have a hardness from about 20 to about 40 as measured on the Shore
D scale and a flexural modulus from about 2,000 to about 10,000 psi
as measured in accordance with ASTM method D-790.
More particularly, the present inventors have discovered that if
relatively low amounts of the above indicated soft ionomers are
utilized with the specific hard ionomers described above, in the
combinations more clearly defined below and demonstrated in the
Examples, the overall combinations, when utilized for golf ball
construction, produce golf balls having higher coefficient of
restitution values (i.e. longer distance) at similar compression
values than golf balls produced by known hard-soft ionomer blends,
including the hard-soft ionomer blends utilized to produce
Spalding's current Tour Edition.RTM. 100 ball (i.e. U.S. Pat. No.
4,884,814).
In this regard, the inventors have found that when the
ethylene-acrylic acid based soft ionomer resins recently developed
by the Exxon Corporation under the designation "Iotek 7520"
(referred experimentally by differences in neutralization and melt
indexes as LDX 195, LDX 196, LDX 218 and LDX 219) and more
preferably, the ethylene-methacrylic acid based soft-ionomers sold
by Dupont under the designations "Surlyn.RTM. 8625" and
"Surlyn.RTM. 8629" are combined with the known hard ionomers
indicated above, the combination produces higher C.O.R. values at
equal or similar compression.
While the exact chemical composition of the resins to be sold by
Exxon under the designation Iotek 7520 is considered by Exxon to be
confidential and proprietary information, Exxon's Experimental
Product Data sheet lists the following physical properties of the
ethylene acrylic acid zinc ionomer developed by Exxon:
TABLE 3 ______________________________________ Property ASTM Method
Units Typical Value ______________________________________ Physical
Properties of Iotek 7520 Melt Index D-1238 g/10 min. 2 Density
D-1505 kg/m.sup.3 0.962 Cation Zinc Melting Point D-3417 .degree.C.
66 Crystallization D-3417 .degree.C. 49 Point Vicat Softening
D-1525 .degree.C. 42 Point Plaque Properties (2 mm thick
Compression Molded Plaques) Tensile at Break D-638 MPa 10 Yield
Point D-638 MPa None Elongation at Break D-638 % 760 1% Secant
Modulus D-638 MPa 22 Shore D Hardness D-2240 32 Flexural Modulus
D-790 MPa 26 Zwick Rebond ISO 4862 % 52 De Mattia Flex D-430 Cycles
>5000 Resistance ______________________________________
In addition, test data collected by the inventors indicates that
Iotek 7520 resins have Shore D hardnesses of about 32-36 (per ASTM
D-2240), melt flow indexes of 3.+-.0.5 g/10 min (at 190.degree. C.
per ASTM D-1288), a flexural moduluses of about 2500-3500 psi (per
ASTM D-790). Furthermore, testing by an independent testing
laboratory by pyrolysis mass spectrometry indicates that the Iotek
7520 resins are generally zinc salts of a terpolymer of ethylene,
acrylic acid, and methyl acrylate.
Examples of the more preferred methacrylic acid based soft (low
modulus) ionomer resins suitable for use in the invention include
Surlyn.RTM. 8625 and Surlyn.RTM. 8629. The typical properties of
these ionomers are listed below:
TABLE 4 ______________________________________ Typical Properties
of Surlyn .RTM. Low Modulus Ionomer Resins Typical Properties
ASTM-D AD-8265 AD-8629 ______________________________________
Cation Type Sodium Sodium Melt Flow Index, gms/10 min. D-1238 0.9
0.9 Specific Gravity D-792 0.94 0.94 Hardness, Shore A/D 92/39
84/25 Tensile Strength, (kpsi) MPa D-638 (4.2) 28.8 (3.1) 21.2
Elongation, % D-638 660 770 Flexural Modulus, (kpsi) MPa D-790
(7.1) 49.1 (2.8) 19.3 Tensile Impact (23.degree. C.) KJ/m.sup.2
D-18225 494 (235) 447 (213) (ft-lbs/in.sup.2) Melting Point,
.degree.C. DTA 81 72 Freezing Point, .degree.C. DTA 51 38 Vicat
Temperature, .degree.C. D-1525 51 48
______________________________________
The superior golf balls of the present invention containing the
improved hard-soft ionomer blends can be generally produced from a
central core and an outer cover wherein the outer cover is made
from a composition comprised of a blend of from about 90 to about
70 weight percent of a hard ionomer, and from about 10 to about 30
weight percent of a soft ionomer, preferably a methacrylic acid
soft ionomer.
More preferably, it has been found that a golf ball exhibiting
properties of enhanced travel distance (i.e. higher C.O.R. values)
with similar or improved playability (i.e. compression
characteristics etc.) without a sacrifice in durability, can be
produced from a core and a cover, wherein the cover is made from a
composition comprised from about 90 weight to about 75 percent of a
hard ionomer resin, and from about 10 to about 25 weight percent of
a soft ionomer, preferably a methacrylic acid soft ionomer.
Additional materials may also be added to the compositions of the
present invention, including dyes (for example, Ultramarine Blue
sold by Whitaker, Clark, and Daniels of South Plainsfield, N.J.)
(see U.S. Pat. No. 4,679,795), pigments such as titanium dioxide,
zinc oxide, barium sulfate and zinc sulfate; UV absorbers;
antioxidants; antistatic agents; and stabilizers. Moreover, the
cover compositions of the present invention may also contain
softening agents, such as plasticizers, processing aids, etc., and
reinforcing materials such as glass fibers and inorganic fillers,
as long as the desired properties produced by the golf ball covers
of the invention are not impaired.
The cover compositions of the present invention may be produced
according to conventional melt blending procedures. Generally, the
hard ionomer resins are blended with the soft ionomeric resins in a
Banbury type mixer, two-roll mill, or extruder prior to molding.
The blended composition is then formed into slabs and maintained in
such a state until molding is desired. If necessary, further
additives such as inorganic fillers, antioxidants, stabilizers,
and/or zinc oxide may be added and uniformly mixed before
initiation of the molding process.
The golf balls of the present invention can be produced by molding
processes currently well known in the golf ball art. Specifically,
the golf balls can be produced by injection molding or compression
molding the novel cover compositions about wound or solid molded
cores to produce a golf ball having a diameter of about 1.680
inches and weighing about 1.620 ounces. The standards for both the
diameter and weight of the balls are established by the United
States Golf Association (U.S.G.A.). Although both solid core and
wound cores can be utilized in the present invention, as a result
their lower cost and superior performance, solid molded cores are
preferred over wound cores.
Conventional solid cores are typically compression molded from a
slug of uncured or lightly cured elastomer composition comprising a
high cis content polybutadiene and a metal salt of an .alpha.,
.beta., ethylenically unsaturated carboxylic acid such as zinc mono
or diacrylate or methacrylate. To achieve higher coefficients of
restitution in the core, the manufacturer may include a small
amount of a metal oxide such as zinc oxide. In addition, larger
amounts of metal oxide than are needed to achieve the desired
coefficient may be included in order to increase the core weight so
that the finished ball more closely approaches the U.S.G.A. upper
weight limit of 1.620 ounces. Other materials may be used in the
core composition including compatible rubbers or ionomers, and low
molecular weight fatty acids such as stearic acid. Free radical
initiator catalysts such as peroxides are admixed with the core
composition so that on the application of heat and pressure, a
complex curing or cross-linking reaction takes place.
The term "solid cores" as used herein refers not only to one piece
cores but also to those cores having a separate solid layer beneath
the cover and above the core as in U.S. Pat. No. 4,431,193, and
other multilayer and/or non-wound cores.
Wound cores are generally produced by winding a very large elastic
thread around a solid or liquid filled balloon center. The elastic
thread is wound around the center to produce a finished core of
about 1.4 to 1.6 inches in diameter, generally. Since the core
material is not an integral part of the present invention, a
detailed discussion concerning the specific types of core materials
which may be utilized with the cover compositions of the invention
are not specifically set forth herein. In this regard, the cover
compositions of the invention may be used in conjunction with any
standard golf ball core.
As indicated, the golf balls of the present invention may be
produced by forming covers consisting of the compositions of the
invention around cores by conventional molding processes. For
example, in compression molding, the cover composition is formed
via injection at about 380.degree. F. to about 450.degree. F. into
smooth surfaced hemispherical shells which are then positioned
around the core in a dimpled golf ball mold and subjected to
compression molding at 200.degree.-300.degree. F. for 2-10 minutes,
followed by cooling at 50.degree.-70.degree. F. for 2-10 minutes,
to fuse the shells together to form an unitary ball. In addition,
the golf balls may be produced by injection molding, wherein the
cover composition is injected directly around the core placed in
the center of a golf ball mold for a period of time at a mold
temperature of from 50.degree. F. to about 100.degree. F. After
molding the golf balls produced may undergo various further
processing steps such as buffing, painting, and marking.
The resulting golf balls produced from the novel hard-soft
ionomeric resin combinations of the present invention exhibit
enhanced distance and playability properties over the art without
sacrificing durability. This is due to the use of methacrylic acid
based ionomers as the soft ionomer in the overall cover stock
composition.
The present invention is further illustrated by the following
examples in which the parts of the specific ingredients are by
weight. It is to be understood that the present invention is not
limited to the examples, and various changes and modifications may
be made in the invention without departing from the spirit and
scope thereof.
EXAMPLES
By blending the ingredients set forth in the Tables below, a series
of cover formulations were produced. In the examples, cover
formulations containing the soft ionomer-hard ionomer blends of the
present invention (Examples 2-5 and 9-20) were compared with the
hard-soft ionomer blends of the prior art including the hard-soft
ionomer blends utilized to produce the current Top Flite.RTM. XL II
(see Example 1) which is the subject of U.S. Pat. No. 4,911,451,
the current Tour Edition.RTM. 100 ball (see Example 8) which is the
subject of U.S. Pat. No. 4,884,814, and the current Tour
Edition.RTM. 90 ball (Example 7) which is the subject matter of
co-pending U.S. application Ser. No. 559,177.
In addition, the properties produced by the cover compositions
formulated with the soft ionomer-hard ionomer blends of the present
invention (Examples 2-5 and 9-20) were compared to the properties
produced by the commercial representatives of the Tour
Edition.RTM., Tour Edition.RTM. 100 and the Top Flite.RTM.II balls
currently being sold by Spalding & Evenflo Companies, Inc.,
Tampa, Fla., as well as a wide variety of competitive golf balls
available in the market place.
Along this line, the current Tour Edition.RTM. ball is unique in
that it is a two piece (solid core, molded cover) ball that meets
the needs of golfers who demand superior control, historically
obtained only with balata covered wound balls. It offers superior
playability at the sacrifice of coefficient of restitution, which
relates directly to distance.
The Tour Edition.RTM. 100 ball has a slightly softer cover than the
Tour Edition.RTM. ball and utilizes a unique octahelix dimple
design. The Tour Edition.RTM. 100 ball more closely meets the
demands of the pro tour golfer than any other Spalding ball
previously produced.
The Top Flite.RTM. ball is considered to be a "hard" Surlyn or
Iotek ionomeric resin ball. As a result of the ball's hardness, the
Top Flite.RTM. ball is a difficult ball for golfers to control.
Generally, the harder the golf ball, the more difficult it is for a
golfer to impart spin to the ball, and hence, control the ball
during flight. However, as a result of its outstanding durability
and maximum distance, the ball is widely accepted by a large
percentage of golfers.
The present invention is directed to various blends of hard
ionomers and soft ionomers, which, when utilized for golf ball
cover construction, produce intermediate modulus golf balls closely
approaching the superior distance properties exhibited by the
current Top Flite.RTM. ball without sacrificing the playability
characteristics of the current Tour Edition.RTM. ball.
The cover formulations set forth below in Tables 5 and 6 were
injection molded at 400.degree. F. around identical solid type
cores having a finished diameter of 1.545 inches to produce golf
balls approximately 1.680 inches in diameter having nominal cover
thickness of 0.0675 inches. The properties of Riehle compression,
coefficient of restitution (C.O.R.), Shore Hardness, impact
resistance, and spin rate for the cover formulation were
determined. The data for each example represents the average data
for one dozen balls produced according to the desired manner. The
properties were measured according to the following parameters:
Riehle compression is a measurement of the deformation of a golf
ball in inches under a fixed static load of 225 pounds.
Coefficient of restitution (C.O.R.) was measured by firing the
resulting golf ball is an air cannon at a velocity of 125 feet per
second against a steel plate which is positioned 12 feet from the
muzzle of the cannon. The rebound velocity was then measured. The
rebound velocity was divided by the forward velocity to give the
coefficient of restitution.
Shore hardness was measured in accordance with ASTM Test 2240.
Cut resistance was measured in accordance with the following
procedure: A golf ball is fired at 135 feet per second against the
leading edge of a pitching wedge, wherein the leading edge radius
is 1/32 inch, the loft angle is 51 degrees, the sole radius is 2.5
inches, and the bounce angle is 7 degrees.
The cut resistance of the balls tested herein was evaluated on a
scale of 1-5. 1 represents a cut that extends completely through
the cover to the core; a 2 represents a cut that does not extend
completely through the cover but that does break the surface; a 3
does not break the surface of the cover but does leave a permanent
dent; a 4 leaves only a slight crease which is permanent but not as
severe as 3; and a 5 represents virtually no visible indentation or
damage of any sort.
The spin rate of the golf ball was measured by striking the
resulting golf balls with a pitching wedge or 9-iron wherein the
club-head speed is about 80 feet per second and the ball is
launched at an angle of 26 to 34 degrees with an initial velocity
of about 110-115 feet per second. The spin rate was measured by
observing the rotation of the ball in flight using stop action
Strobe photography.
Initial velocity is the velocity of a golf ball when struck at a
hammer speed of 143.8 feet per second in accordance with a test as
prescribed by the U.S.G.A.
TABLE 5 ______________________________________ Formulations 1 2 3 4
5 6 7 8 ______________________________________ Ingredients Surlyn
.RTM. -- 7.0 10.5 17.5 21.0 35.0 -- 49.1 8269 Surlyn .RTM. -- 3.0
4.5 7.5 9.0 15.0 -- 21.4 8625 Surlyn .RTM. -- 60.2 56.5 49.0 45.3
30.3 -- 15.2 9910 Surlyn .RTM. -- 20.2 18.9 16.4 15.1 10.1 -- 4.7
8940 2714 White -- 9.6 9.6 9.6 9.6 9.6 -- 9.6 MB.sup.1 Iotek 8000
45.2 -- -- -- -- -- 22.7 -- Iotek 7030 45.2 -- -- -- -- -- 22.7 --
Iotek 7520 -- -- -- -- -- -- 45.0 -- 2810 White 9.6 -- -- -- -- --
9.6 -- MB.sup.2 Properties Weight, 45.1 45.3 45.2 45.1 45.3 45.4
45.1 45.2 grams Riehle 56 59 60 62 61 61 64 64 Compression C.O.R.
.824 .815 .812 .809 .808 .804 .800 .801 Shore D 56 59 60 62 61 61
64 64 Hardness Cut Resist- 4-5 4-5 4-5 4-5 4 3-4 3-4 3-4 ance (5 =
No visible mark) (1 = Clean cut through cover) Spin Rate 6,255
7,744 7.986 8,339 8,383 8,856 9,246 8,966 (RPM) (Tour Edition #9
Iron) ______________________________________ Also tested: Titleist
(Balata) Tour 100: .784 C.O.R. 9,397 RPM 1-2 cut Titleist DT 90:
.789 C.O.R. 7,658 RPM 4-5 cut Titleist DT 100: .799 C.O.R. 7,928
RPM 4-5 cut (RPM) ______________________________________ .sup.1
2714 White MB (Master Batch) is comprised of 75.85% Surlyn .RTM.
8528, 23.77% Unitane 0-110, 0.05% Ultra Blue, 0.22% Unitex O.B. and
0.03% Santonox R. .sup.2 2810 White MB (Master Batch) is comprise
of 75.85% Iotek 7030, 23.77% Unitane 0-110, 0.05% Ultra Blue, 0.22%
Unitex O.B., and 0.03% Santonox R.
TABLE 6
__________________________________________________________________________
Formulations 9 10 11 12 13 14 15 16 17 18 19 20
__________________________________________________________________________
Ingredients Surlyn .RTM. 8269 17.5 25.0 -- 7.0 8.8 10.5 12.3 14.0
15.8 19.3 15.0 -- Surlyn .RTM. 8265 7.5 -- 25.0 3.0 3.7 4.5 5.2 6.0
6.7 8.2 -- 15.0 Surlyn .RTM. 9910 49.0 49.0 49.0 60.2 58.4 56.5
54.6 52.7 50.9 47.1 56.5 56.5 Surlyn .RTM. 8940 16.4 16.4 16.4 20.2
19.5 18.9 18.3 17.7 17.0 15.8 18.9 18.9 2714 White MB 9.6 9.6 9.6
9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 Properties Weight, grams 45.0
45.1 44.9 45.1 45.1 45.1 45.1 45.1 45.3 45.1 45.2 45.1 Riehle 64 64
63 62 61 62 62 62 63 64 62 61 Compression C.O.R. .805 .802 .807
.809 .809 .807 .806 .807 .804 .802 .807 .808 Shore D 61 61 59 62 60
63 61 61 60 60 62 62 Hardness Cut Test 4/4 34/5 4/5 4/5 4/5 4/5 4/5
4/5 4/5 4/5 4/5 4/5 Spin rate 8610 8552 8695 8390 8250 8506 8424
8392 8604 8875 8396 8306 (RPM, 9 Iron)
__________________________________________________________________________
Additional Balls Tested: Spin (RPM) Shore D Hardness Cut
__________________________________________________________________________
Titleist Tour 100 Balata 9812 50 4/5 Titleist DT 90 8485 66 4/5
Tour Edition 100 9947 52 4/5 Tour Edition 90 9765 54 4/5 Top-Flite
XL II 7479 65 4/5
__________________________________________________________________________
DISCUSSION OF THE EXAMPLES
The above Examples indicate that use of relatively low amounts of
soft ionomers (i.e. from about 10 to about 25-30 percent) in
combination with relatively large amounts of hard ionomers (i.e.
from about 70-75 to about 90%) produces golf balls exhibiting
higher C.O.R. values (i.e. thus better distance) while maintaining,
and in some instances slightly improving the compression and
playability characteristics of the balls.
In addition, as it can be seen when comparing Examples 6 and 8
(i.e. U.S. Pat. No. 4,884,414) with Examples 2-5 (the present
invention), the balls of the '814 patent produced enhanced spin
properties versus the present invention. However, the enhanced spin
rates of the '814 patent were produced at the expense of C.O.R.
(and hence distance) and cut resistance.
Furthermore, when the balls of the present invention (i.e. Examples
2-5) containing relatively low amounts of soft ionomer resins
(preferably methacrylic acid based soft ionomers) were compared
with the balls comprised of 100% hard ionomer resin (Example 1),
the balls of the present invention produced greatly enhanced spin
characteristics, although some loss in distance was also noted.
Examples 2-5 in Table 5 and Examples 9-20 in Table 6 also indicate
that a slight decrease in C.O.R. and an increase in spin occurs as
the amount of the soft ionomer was increased. Along this line, the
data shows that the addition of only 10 percent of the soft ionomer
(see Example 12) was enough to produce spin rates much higher than
balls deficient in soft ionomer content (i.e. the Top-Flite.RTM. XL
II ball).
The data suggests that the preferred range of the present invention
is from about 10 to about 30 percent of soft ionomer, a more
preferred range being from about 10 to about 25 percent of soft
ionomer, and a most preferred range being about 25 percent of soft
ionomer (i.e. examples 4 and 9).
In addition, when comparing the spin rates and C.O.R. values of the
balls of the present invention with the Titleist.RTM. DT 90 and the
Titleist.RTM. DT 100 balls (i.e. the ionomer resin-covered wound
balls trademarked and sold by the Acushnet Co.), a significant
advantage in distance (higher C.O.R. values) and/or spin rates were
observed without any significant decreases in durability (i.e. cut
resistance, etc.) being noted. Consequently, while the
Titleist.RTM. DT balls are reportedly advantageous as a result of
the use of the wound versus solid core (i.e. because the wound core
is softer than the solid core, the softer core is said by Acushnet
to have the ability to deform, thereby giving better control to the
golfer) the test results indicated that the present invention
produces substantially similar playability characteristics at much
longer distances.
In addition to the above indicated test results, the distance and
playability properties of the more preferred formulations of the
present invention (i.e. Examples 4 and 9), which are representative
of the chemical composition of Spalding's new, longer distance and
slightly softer, Top Flite.RTM. Tour 90 golf balls (i.e. Top
Flite.RTM. Tour XL, Top Flite.RTM. Tour 90 and Top Flite.RTM. Tour
Plus 90 based upon differences in dimple patterns) were compared
with various combinations of Spalding's current Top Flite.RTM. golf
balls having similar dimple patterns (i.e. Top Flite.RTM. XL, Top
Flite.RTM. II and Top Flite.RTM. Plus golf balls), as well as a
number of competitive golf balls, such as Titleist.RTM. DT 90. The
following performance results were produced:
TABLE 7 ______________________________________ Distance Test
Conditions Before Test After Test:
______________________________________ Launch Angle - degrees 8.9
N/A Bill Speed - fps 214.2 N/A Spin Rate - rpm 2850 N/A Turf
Condition FIRM FIRM Wind - mph/dir. 0/0 0/0 Temp/RH - det/% 99/48.4
100/50 ______________________________________ Test Results Car- To-
To- Ball Flight Car- ry Ctr tal tal Type Traj Time ry Diff Dev Roll
Dist Diff ______________________________________ TFXL- 12.7 6.0
229.5 -0.9 6.17 29.3 258.8 -2.9 CON TFII- 12.2 5.9 228.7 -1.7 6.21
33.0 261.6 0.0 CON TFPL- 12.4 5.9 229.4 -1.0 7.13 28.2 257.6 -4.0
CON TOUR- 12.7 6.0 230.4 0.0 7.00 30.3 260.7 -1.0 XL90 TOUR90 11.9
5.8 227.5 -2.9 4.29 31.8 259.3 -1.8 PLUS90 12.2 5.8 227.8 -2.6 6.67
32.3 259.9 -1.8 TITDT- 12.6 6.2 226.8 -3.5 8.8 23.2 250.0 -11.6 90
______________________________________ KEY TO BALL TYPES: TFXLCON =
TFXL CONTROL (410 Hex Dimple) TFIICON = TF II CONTROL (422 Octa
Dimple) TFPLCON = TF PLUS CONTROL (422 Tri Dimple) TOURXL90 = TF
TOUR XL 90 (422 Hex Dimple) TOUR90 = TF TOUR 90 (422 Hex Dimple)
PLUS90= TF TOUR PLUS 90 (422 Tri Dimple) TITDT90 = TITLEIST DT
90
The distance testing demonstrated a 9-10 yard advantage of the
present invention over the Titleist.RTM. DT ball, a ball
demonstrating comparable spin characteristics to the balls of the
present invention. Furthermore, the distance test demonstrated that
the balls of the invention produced relatively similar distance
data when compared to the balls of U.S. Pat. No. 4,911,451, while
exhibiting greatly enhanced playability (spin rates, compression
etc.) properties.
As a result, the new hard-soft ionomer blends of the present
invention produce golf balls exhibiting properties of enhanced
distance and playability without sacrificing durability.
The invention has been described with reference to the preferred
embodiment. Obviously, modifications and alterations will occur to
others upon reading and understanding the preceding detailed
description. It is intended that the invention be construed as
including all such modifications and alterations insofar as they
come within the scope of the appended claims or the equivalents
thereof.
* * * * *